At present, surgical intervention offers the best outcome for Moyamoya disease. If the patient has already suffered major strokes then the surgical outcome and improvement is not good. It needs to be done early in the course of the disease when the diagnosis is made

The Moyamoya Disease is a rare vascular disease which affects the brain. This disease is commonly seen in children between five-10 years of age and in adults between 35-50 years of age. Though certain genes have been linked to the disease, the exact cause remains elusive. In India, this disease is frequently seen in denizens of West Bengal and North East India.

This condition causes a progressive slow narrowing of major intracranial blood vessels which supplies blood to both hemispheres of the brain. The body tries to compensate for the reduced blood supply by opening up previously nonfunctioning small vascular connections between the adjacent blood vessels in order to improve the blood supply. Despite the best efforts, as the disease progresses, the blood supply to the brain progressively diminishes and a stage of decompensation occurs. There is an imbalance between blood oxygen supply and the demand of the brain. In the above event the patient starts experiencing initially fleeting neurological deficits leading to symptoms such as weakness, headaches, seizures which inevitably worsens and ends in permanent neurologic deficits of varying degrees.

Diagnosis of Moyamoya disease is mainly done with MRI and MR angiogram (MRA) or CT angiogram. The MRI shows the presence of any infarctions or bleed and presence of significant brain damage. MRA reveals the brain blood vessels patency and caliber. It demonstrates the narrowing of blood vessels and the presence of opened up vascular channels trying to shore up the brain blood supply. When the diagnosis cannot be made with certainty on MRI, a slightly invasive procedure known as digital subtraction angiogram (DSA) will be needed. It is the gold standard and can establish the diagnosis irrefutably. Ancillary tests like SPECT scans may be done in certain cases to demonstrate functionally the adequacy of blood supply.

Management of Moyamoya disease

• Untreated patients have a poor prognosis with major neurologic deficits, including death occurring in 70-75 per cent by two years.
• Medical management includes blood thinning tablets (aspirin and clopidogrel) to prevent formation of small clots which may block the already compromised narrow blood vessels and cause stroke. However though medications intuitively seem to reduce the risk of future stroke, it does not prevent the progression of the disease and a substantial number of patients develop strokes in the months or years ahead.
• Surgical intervention consists of augmenting the intracranial blood supply by using the blood vessels on the scalp. By this procedure there is an immediate and a delayed increase in blood supply to the brain which offsets the progressive oxygen deficit the brain will face due to the ongoing progressive occlusion of the intracranial blood vessels.
• The surgical procedures include a direct bypass between a scalp vessel (superficial temporal artery) and an intracranial vessel (branch of middle cerebral artery) and indirect procedures like placing the temporalis muscle directly on the brain surface. The direct surgery improves the blood supply immediately and the indirect procedures result in slow parasitisation of the muscle blood supply by the brain.
• At present, surgical intervention offers the best outcome for Moyamoya disease. If the patient has already suffered major strokes then the surgical outcome and improvement is not good. It needs to be done early in the course of the disease when the diagnosis is made. Surgery prevents development of stroke and neurologic deficits, but cannot undo the damage of an already sustained stroke.

The writer is Dr Dhananjaya I Bhat ,Senior Consultant Neurosurgery at Aster RV Hospital